Need help with accurate timers for multithreaded programs on Linux/X-86

Hi Folks,
  I will appreciate if people can point me to accurate and reliable 
timers for multithreaded programs on Linux/X-86 (specifically RH9.0).

I have quite a bit of multithreading experience (mainly on Solaris)
but very little on Linux.  On Solaris, the two timers: gethrvtime()
and gethrtime() are proving to be very valuable in tuning/testing
the code that I am currently multithreading.

On Linux, I have tried both gettimeofday based timer and a timer 
using RDTSC instruction in IA-32 but am not able to get repeatable
and reliable timings with these...well bottomline is that we are
seeing reasonable scaling (eg. 1.6-1.7X on 2-way) on Solaris (version 8)
but basically none on Linux (RH 9.0).  I suspect my lack of 
experience on Linux is probably the reason...hence request for
help from you all. 

I know this is a very general question but any pointers you all
can provide on how to accurately measure time in portions of
code (on a per-thread basis) and/or if I should try a different 
version of Linux thread library will be really appreciated.

regards,

--Rajat